In view of the needs of the circuit design, element characteristics and the like, the patterns of elements, wirings, electrodes, and the like, which form semiconductor devices, are arranged. Accordingly, a fraction (pattern-covering fraction) indicating how much area of the plane region of the semiconductor device is occupied by these pattern areas differs depending on each semiconductor device. Moreover, these pattern areas also differ in the plane region of the semiconductor device in many cases.
When the pattern-covering fraction differs in the plane region of the semiconductor device, the following problems occur in the semiconductor manufacturing processes. For example, when insulating gate field effect transistors (MOSFETs) are arranged as elements in a logic circuit or the like, the space between MOSFETs is relatively increased to form a large element isolation region.
In such a case, in the manufacturing process, burying an insulating layer between wirings by use of, for example, chemical mechanical polishing process or the like, may cause a phenomenon in which a relatively large insulating layer isolation region is deeply polished, and may cause a reduction in yield. Moreover, the pattern-covering fraction in the vicinity of the pattern differs in fine patterning processes such as lithography, relative ion etching, and the like, causing a possibility that non-uniformity in the size and the shape may occur.
In order to avoid such problems, there is used a method in which a dummy pattern having no function as an element in addition to an actual pattern which is originally necessary for an element, is formed to make the pattern-covering fraction uniform in a mask pattern design. For forming the dummy pattern, the following process is known. First, the dummy pattern prohibition region is formed on a portion where the actual pattern already exists or in the vicinity thereof. Sequentially, the dummy pattern is arranged on a dummy pattern region to make the pattern-covering fraction uniform.
With miniaturization of the element, more precise control on uniformity such as film thickening of a thin film in the semiconductor device is required in manufacturing processes. However, in the conventional dummy pattern forming method, the uniform pattern-covering fraction is required over the entire dummy pattern region, causing a problem in which the pattern-covering fraction in the vicinity of the dummy pattern prohibition region is reduced to make it impossible to form a dummy pattern having a pattern-covering fraction with high uniformity. This causes non-uniformity in the size and the shape for example.